It has long been a common medical practice to use guidewires in the placement of catheters in a patient's blood vessels. With a guidewire in place in the blood vessel, a catheter can be threaded and advanced over the guidewire thus guiding the catheter to the intended vascular site. The guidewire serves to center the catheter within the blood vessel and reduces the risk of trauma to the blood vessel by the advancing catheter. The use of a guidewire also enables the catheter to be advanced through the blood vessel relatively quickly, thereby reducing the time required for the procedure.
A standard guidewire typically is slightly longer than the catheter with which it is to be used. For example, with an angiographic catheter of the order of 130 cm long, the guidewire typically may be of the order of 145 cm to 175 cm long. When the catheter is in place over the guidewire, a relatively short portion of the guidewire protrudes proximally from the catheter. That enables the guidewire to be manipulated, if desired, from its protruding proximal end. In that regard, it may be noted that the guidewire may be of a steerable construction in which a bend is formed in its distal tip and the direction in which the bent distal tip extends is controlled by rotating the guidewire from its proximal end. For example, the guidewire may be of the type described in U.S. Pat. No. 4,545,390.
In many vascular catheterization procedures, it may become necessary to change catheters during the procedure. Usually, it is preferred that the catheter be removed in a manner which enables a guidewire to remain in place in the blood vessel so that the next succeeding catheter in the procedure can be inserted into the blood vessel, over the guidewire to guide the catheter to the intended site in the blood vessel. In order to maintain a guidewire in place while withdrawing the catheter, the guidewire must be gripped at its proximal end to prevent it from being pulled out of the blood vessel together with the catheter. The catheter, however, is longer than the proximal portion of the guidewire which protrudes out of the patient. Thus, before the catheter is fully withdrawn, it completely covers the proximally extending end of the guidewire. As a result, a standard guidewire cannot be held in place to prevent it from being withdrawn together with the catheter.
Among the techniques for effecting a catheter exchange has been to use an exchange guidewire. The exchange guidewire typically is about 300 cm long, much longer than the typically standard guidewire. The structure of the standard and exchange wires typically is the same except for the length. The additional length of the exchange wire results in a long proximally protruding portion that is longer than the catheter to be removed. When the catheter is removed, some part of the proximally extending portion of the exchange wire will always be exposed to provide a means by which the exchange wire can be gripped and its position in the blood vessel maintained. Use of the exchange wire reduces the risk of trauma to the patient because it is placed while the first catheter remains in the patient. Thus, the procedure involves initial removal of the standard guidewire from the catheter while the catheter remains in place in the patient. Then the exchange wire is advanced through the catheter to replace the original guidewire. Because the exchange wire is guided through the patient's blood vessel by the first catheter, it does not contact the lumen of the blood vessel, except, perhaps, for a small portion which protrudes distally of the first catheter. The original catheter then is withdrawn over the exchange wire which is maintained in place in the blood vessel. The next succeeding catheter then can be inserted into the patient over the exchange wire.
The foregoing system and technique of using a long exchange wire is not free from difficulty. The proximally extending end of the exchange wire is quite long and cannot be manipulated easily. Typically one member of the medical team involved in the procedure must stand back from the procedure in order to hold the long "tail" (the proximal end) of the guidewire. Additionally, should it be desirable to manipulate the exchange wire, for example, to steer it to a repositioned location, the long trailing end, the exchange wire makes it difficult to manipulate and rotate. Typically, after a catheter exchange has been performed with an exchange wire, the exchange wire is removed and is replaced with a shorter length guidewire that is more easily manipulated by the physician. That, however, adds time and complexity to the procedure.
It would be desirable, therefore, to provide an exchange guidewire that avoided the foregoing difficulties. It is among the general objects of the invention to provide such a guidewire.